Pass alias suffix to index script, optionally skip aliasing

See #191

This pull request fixes an issue with the automatic alias updates: after indexing lobid-resources, the alias was updated before lobid-items were indexed into the same index, resulting in an incomplete index until indexing lobid-items was done.

This pull request also simplifies the alias handling: previously, there was a custom mapping from index names to aliases. Instead, we now just remove the timestamp from the index name to create the alias.